spec: allow disallow of \uFFFD in import path
spec: allow disallow of \uFFFD in import path

Turns out U+FFFD is a graphic character too.

http://play.golang.org/p/YblCfKAfko

R=gri
CC=golang-dev
http://codereview.appspot.com/5699052

wesolows/golang,firebitsbr/golang-old,firebitsbr/golang-old,firebitsbr/golang-old,firebitsbr/golang-old,wesolows/golang-old,firebitsbr/golang-old,wesolows/golang-old,firebitsbr/golang-old,wesolows/golang,wesolows/golang,wesolows/golang-old,wesolows/golang-old,firebitsbr/golang-old,wesolows/golang-old,wesolows/golang,wesolows/golang,wesolows/golang-old,wesolows/golang-old,firebitsbr/golang-old,wesolows/golang,wesolows/golang